1. Field of the Invention
The present invention relates to reclosable plastic bags of the type in which perishable food products and other goods are packaged for sale to consumers in retail outlets. More specifically, the present invention relates to reclosable plastic bags manufactured and concurrently filled on horizontal or vertica form-fill-and-seal (FFS) machines, wherein a plastic interlocking zipper for each bag is disposed transversely relative to the direction of motion of the thermoplastic sheet material used to form the reclosable bags on the FFS machine.
2. Description of the Prior Art
The present invention relates to improvements in the package-making art and may be practiced in the manufacture of thermoplastic bags and packages of the kind t at are used for various consumer products, but which are particularly useful for food products which must be kept in moisture- and air-tight packages, free from leakage before initially being opened for access to the product contents, which packages are then reclosable by zipper means to protect any remainder of the product therein.
The indicated art is fairly well-developed, but nevertheless remains open to improvements contributing to increased efficiency and cost effectiveness.
One problem that still hampers the production of packages from continuous zipper-equipped sheet material is the difficulty in attaining a satisfactory sealing of the bag or package against leakage, where the zipper extends through the side (cross) seal areas separating one bag or package from the next. The problem occurs where the zipper is longitudinal with respect to the direction of motion of the thermoplastic sheet material used to form the reclosable bags on the FFS machine, in which case the transverse, or side, sealing bars must flatten and seal the zipper at the same time as they are sealing the thermoplastic sheet material from which the packages are being made. The relatively high percent age of packages of this type which leak attests to the difficulty with which this is consistently and success fully achieved.
Numerous attempts have been made to solve this problem. Among the approaches that have been taken is the substitution of a transverse zipper for the longitudinal zipper. Where such a zipper is provided, the transverse sealing bars associated with the FFS machine do not flatten the zipper as they are making side seal, although they may seal the zipper to the thermoplastic sheet material transversely thereacross without flattening it.
The present invention relates to reclosable plastic bags or packages having transverse zippers. Where packages of this type are used to retail certain consumer products, such as snack foods, there is a preference among consumers for a package which may be initially opened by pinching its opposed side walls between the fingers of opposed hands below the seal at the top of the package, and by pulling the side walls apart to separate the top seal from within the package. This technique is difficult to follow where the zipper is of the type that is easier to open from outside the package, that is, from the consumer side, than from inside the package, that is, from the product side. The present invention is a zipper strip, and a reclosable package incorporating the zipper strip, which has been designed for use in situations where consumers prefer to open the package in this manner.